To inject gaseous fuel into an internal combustion engine, the fuel pressure must be raised higher than the pressure in the piston combustion chamber. For a compression ignition engine, such as a diesel engine, a fuel pressure as high as 200 bar (approx. 3,000 psig) may be required to inject the fuel and to ensure combustion. Compressed gaseous fuel is typically supplied from pressure rated storage vessels carried on board the vehicle. As the fuel is consumed, the pressure in the storage vessels drops. To consistently maintain the pressure of gaseous fuels within a pre-determined acceptable operating range for injection into the combustion chamber of the internal combustion engine, it is necessary to provide a means for increasing the pressure of the gaseous fuel. The pre-determined acceptable operating range is determinable from the optimal injection pressure which depends upon the particular characteristics of a given engine.
An intensifier is a compressor which increases the pressure of a gas supplied from a variable pressure source, such as a tank holding compressed natural gas (CNG) to an end use for the gas, such as an internal combustion engine. It is well known to locate a small accumulator vessel near a fuel injector to maintain the gaseous fuel pressure at the injector within a consistent pre-determined acceptable operating range notwithstanding the varying pressure in the gaseous fuel supply system and storage vessel. When the gas pressure in the accumulator decreases, it is known to use an intensifier to deliver compressed gaseous fuel from the storage vessel to the accumulator vessel. When the pressure in the accumulator rises to the upper limit of the pre-determined acceptable operating range, the intensifier typically shuts off. Accordingly, pressure in the accumulator is kept within a pre-determined acceptable operating range.